A client is admitted to rule out Cushing's syndrome. Which laboratory tests should be anticipated?

A client is admitted to rule out Cushing's syndrome. Which laboratory tests should be anticipated?

• A. Plasma drug levels of quinidine, digoxin, and hydralazine.
• B. Plasma levels of ACTH and cortisol.
• C. A 24-hour urine for metanephrine and catecholamine.
• D. Spot urine for creatinine and WBCs.

Answer: (B)

Ruling out Cushing's involves confirming elevated cortisol and identifying the source by checking ACTH alongside cortisol. Measuring plasma cortisol shows whether cortisol levels are high, while measuring plasma ACTH helps distinguish whether the excess cortisol is ACTH-dependent (from a pituitary or ectopic source) or ACTH-independent (from an adrenal source). This pairing guides the next steps in diagnosis, such as using dexamethasone suppression tests or 24-hour urinary free cortisol, but these two labs are the essential initial tests to anticipate when evaluating suspected Cushing's. The other options focus on different conditions (pheochromocytoma or unrelated urinary findings) and are not appropriate for diagnosing Cushing's syndrome.

Ruling out Cushing's involves confirming elevated cortisol and identifying the source by checking ACTH alongside cortisol. Measuring plasma cortisol shows whether cortisol levels are high, while measuring plasma ACTH helps distinguish whether the excess cortisol is ACTH-dependent (from a pituitary or ectopic source) or ACTH-independent (from an adrenal source). This pairing guides the next steps in diagnosis, such as using dexamethasone suppression tests or 24-hour urinary free cortisol, but these two labs are the essential initial tests to anticipate when evaluating suspected Cushing's. The other options focus on different conditions (pheochromocytoma or unrelated urinary findings) and are not appropriate for diagnosing Cushing's syndrome.